1. Field of the Invention
The present invention relates to a method of purifying RNA using a kosmotropic salt, and more particularly, to a method of purifying a RNA molecule from a biological material including the RNA using a kosmotropic salt on a solid support.
2. Description of the Related Art
A conventional method of separating RNA from a starting material containing the RNA includes guanidinium thiocyanate-phenol-chloroform extraction (so-called Trizol method). In the Trizol method, cells are added into a mixed solution of phenol and guanidine isothiocyanate to lyse the cells, and chloroform is added to the resulting cell lysate to separate the lysate into an aqueous layer and an organic layer, where RNA is in the aqueous layer, protein is in the organic layer, and DNA is at the interface between the aqueous layer and the organic layer. The aqueous layer is then treated with isopropanol.
According to another method for separating RNA, which is disclosed in U.S. Pat. No. 5,234,809, cells are mixed with a chaotropic substance (i.e. a substance which alters the secondary, tertiary and/or quaternary structure of proteins and nucleic acids, but leaving at least the primary structure intact) and a nucleic acid-binding solid phase to produce solid phase-nucleic acid complexes, and the nucleic acid is eluted from the complexes. As chaotropic substance guanidine isothiocyanate or guanidine hydrochloride, sodium iodide may be used and as the solid phase, silicate particles are used.
The methods described above not only use hazardous materials such as phenol, chloroform, and isothiocyanate (which is a chaotropic material), but the RNA obtained contains large amounts of DNA contaminants. Chaotropic materials are known to dehydrate a silica surface to allow nucleic acids to bind to the silica surface by hydrophobic interaction.
U.S. Patent Application Publication No. 2007-0043216 A1 discloses a method of purifying RNA using a buffer (pH<4.5 or pH>7) including a 4-10M RNA-complexing salt such as LiCl, a detergent, and a solid support. The buffer lacks a chaotrope.